public static Task <IEnumerable <Expense> > GetExpensesAsync(this FreeAgentClient client, ExpenseFilter filterBy = ExpenseFilter.All, DateTime?fromDate = null, DateTime?toDate = null)
{
var view = filterBy.GetMemberValue();
return(client.GetOrCreateAsync(c => c.ExpenseList(client.Configuration.CurrentHeader, view, fromDate, toDate), r => r.Expenses));
}